This is standard procedure actually. You have to show that you hold the copyright or they won't publish it. I published a book for an author of a book that's been on the web for years. He (the author) had to fully document that he wrote it or they would have pulled the book -- despite the fact that we had a contract agreement that I was supposed to publish it. They insisted that only the copyright holder can publish under the model we had selected and they made him document it. That policy actually makes sense. There's like 6,000 copies of most public domain books, most of which are easier to read or better formatted for the web.
Remember, UNIX spelled backwards is XINU. -- Mt.